We have incidentally seen that there are quite a number of different operations in which the spinning apparatus takes part. There is the line which most spiders lay down as they wander, and which secures them from the danger of a fall if they lose their footing; there is the snare for catching prey, the nest or retreat, and the egg-cocoon, and in addition, silk from the spinnerets may be used to enwrap and paralyse captured insects, or to assist the young spider to migrate. Since the Epeiridae perform all these operations, and are, moreover, the most finished of snare-makers, it does not surprise us to find in them the highest development of the silk glands and the most complete battery of spools and spigots on the spinnerets. Many spiders, as we know, make no snare at all, and in the case of some, very little spinning is attempted beyond the manufacture of a rather rudimentary covering for the eggs. Naturally a less complex spinning apparatus is required, and we accordingly find that jumping spiders, for instance, have only about fifty silk-glands comprising three different kinds of gland, while the glands found in such of the large Aviculariidae as have been examined have been all alike. There is in some spiders a spinning organ, not to be found in Epeira, which deserves a passing notice. It does not take the place of spinnerets, of which the usual three pairs are present, but it is situated in front of them, and only occurs in the female of the species. Its peculiarity is that the silk does not emerge from projecting spools; but through fine holes in a sieve-like plate, called a _cribellum_, which is flush with the surface of the abdomen. It has no mobility, therefore, and the threads from it have to be combed out and distributed by the spider’s hind leg. For the better accomplishment of this purpose there is a special comb of stiff hairs or bristles, called a _calamistrum_, on each of the fourth pair of legs. The web of these spiders is not unlike that of Agelena, but of a rather finer texture, and it can be seen, on magnification, to consist of an irregular ground-work over which have been spread wavy bands of excessively fine silk, combed out from the orifices of the cribellum glands. Some of these cribellate-spiders, of the genus _Amaurobius_, are not uncommon in our cellars and out-houses; their bodies are of stouter build and their legs much shorter than those of the common house-spider. We have no space for anything approaching a full description of the anatomy of spiders, but there is one other point of structure of which the reader has been promised some account. Attention was directed to the fact that while some spiders are helpless on smooth perpendicular surfaces unless they have lines to cling to, others can run with ease upon the walls or even the ceiling, of a room. [Illustration: Fig. 13. Foot of Jumping Spider (on left), foot of Garden Spider (on right).]